Hi there!
We know that:
Ei = Ef
There is work being done on the object, so:
W = Force · displacement = F · d ⇒ work due to friction
KEi - Fd = KEf (0)
KEi = Fd
Input variables:
1/2mv² = μmgd
Cancel out the mass:
1/2v² = μgd
Solve for d:
1/2(5.3²)/(0.05 · 9.81) = 28.63 m
Answer:
1.a) 1 kJ
1.b) 4 kJ
ratio 1:4
1.c) 4 times as before
2.a) 3.33 m/s2
Explanation:
1.a) bicycle's velocity =Displacement/time
=100/20 m/s
=5 m/s
bicycler's KE =1/2 *mass*(velocity)^2
=1/2*80*5^2
=1000 J = 1 kJ
1.b) bicycle's new velocity =200/20 m/s
=10 m/s
bicycler's new KE =1/2*80*10^2
=4000 J = 4 kJ
Ratio= KE 1 :KE new
= 1 :4
1.c) when bicycler's speed was doubled it increased the KE by 4 times (2^2). because In KE we consider the square of the speed , so the factor we increase the speed , the KE will get increased with the square value of it
ex : speed is triple the prior value , then the KE is as 3^2 times as before. that is 9 times
2.a) car acceleration = (20-0)/6 m/s2
= 3.33 m/s2
